1. Field of the Invention
The present invention relates generally to providing pressurized infusion of liquids and, more particularly, is directed to providing a stable and pressurized flow of irrigation fluid to the eye during surgery.
2. Description of the Background
Certain surgical procedures, such as phacoemulsification surgery, have been successfully employed in the treatment of certain ocular problems, such as cataracts. Phacoemulsification surgery utilizes a small corneal incision to insert the tip of at least one phacoemulsification handheld surgical implement, or handpiece, through the corneal incision. The handpiece includes a needle which is ultrasonically driven once placed within the incision to emulsify the eye lens, or to break the cataract into small pieces. The broken cataract pieces or emulsified eye lens may subsequently be removed using the same handpiece, or another handpiece, in a controlled manner. The surgeon may then insert a lens implant into the eye through the incision. The incision is allowed to heal, and the result for the patient is typically significantly improved eyesight.
As may be appreciated, the flow of fluid to and from a patient through a fluid infusion or extraction system, and thus the control of fluids and fluid pressure through the phacoemulsification handpiece, is critical to the procedure performed. Different medically recognized techniques have been utilized to control the fluid flow during the lens removal portion of the surgery. Among these, one popular technique is a simultaneous combination of phacoemulsification, irrigation and aspiration using a single handpiece. This method includes making the incision, inserting the handheld surgical implement to emulsify the cataract or eye lens, and, simultaneously with this emulsification, having the handpiece provide a fluid for irrigation of the emulsified lens and a vacuum for aspiration of the emulsified lens and inserted fluids.
Currently available phacoemulsification systems, such as those mentioned above, typically include a variable speed peristaltic pump and/or vacuum pump, a vacuum sensor, an adjustable source of ultrasonic power, and a programmable microprocessor with operator-selected presets for controlling aspiration rate, vacuum and ultrasonic power levels. The phacoemulsification handpiece is interconnected with a control console by an electric cable for powering and controlling a piezoelectric transducer that drives the action of the handpiece. Tubing provides irrigation fluid to the eye through the handpiece and enables withdrawal of aspiration fluid from an eye through the handpiece.
Generally, irrigation and aspiration are employed by the surgeon using the device to remove unwanted tissue and maintain pressure within the eye. Moreover, the use of, and particularly the pressurization of, the irrigation fluid is critical and may, for example, prevent the collapse of the eye during the removal of the emulsified lens. Irrigation fluid pressure is also used to protect the eye from the heat generated by the ultrasonic cutting needle and may suspend fragments created during the surgery in fluid for more easy removal through aspiration.
Irrigation fluid pressure has been conventionally handled in two ways. The first method to increase irrigation fluid pressure has relied upon the height of the fluid source. Conventional IV poles may be adjusted in height to create the desired pressure head using gravity-feed principles. The second method includes the use of an infusion pump either directly pumping the fluid typically in the form of a peristaltic pump used in-line with an irrigation delivery line or by pressurizing the fluid container thus increasing higher atmosphere above the fluid resulting in higher infusion pressure and flow to the surgical site.
Although each of the foregoing methods produces pressurized irrigation fluid at the surgical site, each suffers from difficulties in maintaining a constant pressure. For example, infusion pumps must be deployed with a dynamic pressure-sensing control loop to prevent over or under pressurizing the anterior chamber, and may further require venting to control unwanted pressures. Solving these issues may require the use of a special drip spike, a mechanical pressurization compartment, or an over-bag, to control atmospheric pressure. Such solutions add costs and complications to the surgical set-up and to the maintenance of the surgical equipment.
Further, it is typical that the smaller the incision made during surgery, the greater the pressure needed to properly irrigate the surgical site, and gravity-feed systems may not produce the desired amount of pressure due at least to limitations on the height which may be achieved by physically raising the source of irrigation liquid. Typically, the irrigation source is affixed to a movable IV pole which is raised to increase the pressure head. Of course, limitations as to the maximum height of the IV pole and/or the height of overhead objects, such as lights or a ceiling, for example, may limit the amount of achievable height.
Thus, there is a need for a system and method that provides improved pressurized delivery of irrigation fluid to a surgical site.